1. Field of the Invention
This invention pertains to an apparatus and method for effecting repairs to damaged, nonstressed aircraft structure. More specifically, this invention provides a repair to damaged, nonstressed aircraft structure that will withstand a burn requirement established by the Federal Aviation Regulation (FAR 25.855).
2. Description of the Prior Art
There are damaged, non-stressed structures in specific parts of transport aircraft that must be repaired immediately to prevent loss of life and property in the event of a catastrophic situation such as a fire. One such structure is the cargo bay of a transport aircraft. Cargo bays contain a cargo bay liner that is made from high impact resistant and fire resistant material. These cargo liners take considerable abuse from the loading and off loading of cargo at every aircraft terminal. Invariably, in time, a sharp object of cargo will puncture a hole in the liner or damage the liner such that the liner integrity is in question. The FAA regulation effective March, 1991 states that as soon as the damage is discovered, a repair must be made prior:to the next flight. This repair must provide the same burn resistance as the original liner had before the damage. The present invention provides this requirement and can be installed in less than 20 minutes, which can be accomplished, most of the time, between flights.
There are several repair devices and methods available for various types of damaged to aircraft structure. One such method is found in U.S. Pat. No. 4,517,038, which describes a method of repairing ballistic damage to stressed structure. This patent descries a sandwich material of metal, nylon and armid cloth which are heated and fused together to form a strong patch that may be bent to shape like the surface of an airfoil. The patch is then bonded and riveted in place.
Another repair apparatus is described in U.S. Pat. No. 4,858,853. This patent describes a stack of thin flexible metal plates with adhesive applied therebetween. The plates are bent to shape and bolted onto the outside of the aircraft structure. Obviously this is a field repair because a plate bolted on the outside of a wing would cause drag and flow disturbance.
U.S. Pat. No. 4,759,812 discloses a method and apparatus for effecting field repairs in stress carrying structures. This patent describes a patch using two thin metal sheets bent to shape with one part of VELCRO.RTM. bonded to each side. The metal sheets have a resin impregnating the VELCRO.RTM. and when the resin hardens, the patch becomes stiff.
U.S. Pat. No. 3,470,048 describes a method of patching metal car bodies using a metal patch bonded to the body with pressure sensitive film. No mechanical fasteners are used as in the present invention.
U.S. Pat. No. 4,707,391 describes a vehicle body surface repair assembly for automobiles and uses a perforated thin metal or plastic plate. This plate is placed over the damaged part and fiberglass mesh is placed over the plate. Fiberglass body surface repair compound such as Bondo.RTM. is forced in the mesh and perforated plate to better support the repair.
U.S. Pat. No. 3,850,718 uses a metal patch with a thin layer of high density foam bonded to one side. A pressure sensitive adhesive is bonded to the foam which is then applied to the damaged area. This patch finds application in truck trailers and sea going cargo containers.
From the foregoing, the need should be appreciated for a repair patch that will meet the burn requirement of FAR 25.855. The present invention, which is fire resistant, will not loose its integrity even if the adhesive, which is fire retardant, does not hold the patch in place. The fasteners, which will withstand a temperature of at least 1,700 degrees Faherinheit will hold the patch in place and prevent the fire from reaching the aircraft structure. Accordingly, a fuller understanding of the invention may be obtained by refering to the summary of the invention, and the detailed description of the preferred embodiment, in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.